Atom based sensors including atomic clocks and atomic inertial sensors use an alkali metal source that releases alkali metal atoms to form an alkali vapor in a sensing chamber. One type of atom based sensor is a laser cooled sensor. Laser cooled atom based sensors use one or more laser beams directed at the alkali vapor to cool an atomic sample of alkali atoms in the alkali vapor.
Rubidium (Rb) and Cesium (Cs), which are commonly used alkali metals in atom based sensors, have melting points at or below 40 degrees Celsius, and exponentially increasing vapor pressures. Using such an alkali metal in many atom based sensor applications can result in an undesirably high vapor pressure in the sensing chamber. This high vapor pressure results in a large background vapor that collides with the laser cooled atoms and limits the lifetime of the atomic sample.
In order to reduce the background vapor pressure the alkali metal source can be composed of an alkali metal with at least one other element to form an alloy or compound that has a lower vapor pressure at the operating temperature than the alkali metal by itself. The source material can also be composed of a graphite intercalation compound that includes an alkali metal.